This invention relates to position sensing apparatus. British Patent No. 1,551,218 describes apparatus for sensing the position of an object, comprising a moveable member connected to a fixed member by three support units adapted to constrain the members for relative displacement parallel to the three directions respectively of the orthogonal coordinate system, the units being connected in series in a compact box-like arrangement, the moveable member including a stylus for engaging the object, and the apparatus including means for sensing a said relative displacement.
The known apparatus has the advantage of compact construction, but the serial connection of the units has the disadvantage of placing nonuniform loads on the respective units. Also, the units of the known apparatus each comprise two parts constrained for relative parallel displacement by a pair of parallel leaf springs connected to the parts in position therebetween. Such a connection can result in slight tilting of the moveable member when the latter is being displaced. Further, the arrangement of the units in said box-like construction can result in a structure which is relatively complex and can be difficult to produce. It is an object of this invention to overcome at least one of these disadvantages.